Fig. 1.

Oku-okuhachikurou Onsen (OHK), Japan, and the source of Ca. Anthektikosiphon siderophilum. A: Overview map of Japan showing the location of OHK in Akita Prefecture. Modified from Ward et al. (2017a). B: Panorama of OHK pools and channels at the time of sampling. Source pool occurs at the left, with flow downstream to the right. Scale bar ~1 m. Samples were collected from the “Shallow Source” (C, scale bar ~‍ ‍30‍ ‍cm) and “Canal” (D, scale bar ~10‍ ‍cm) sites as scrapings of thin green-colored biofilms overlying iron-oxide and aragonite travertine along the water line.